I just tried this. I got a fresh checkout, no problem. I ran ./bootstrap && ./configure, fine. Then:
zile (master)]$ make
ZLC lib/zmacs/commands.lua
GEN doc/zmacs.1
GEN doc/dotzmacs.sample
GEN lib/zmacs/doc/COPYING.lua
GEN lib/zmacs/doc/FAQ.lua
GEN lib/zmacs/doc/NEWS.lua
help2man: can't get `--help' info from ./lib/zmacs/help2man-wrapper
Try `--no-discard-stderr' if option outputs to stderr
make: *** [doc/zmacs.1] Error 2
make: *** Waiting for unfinished jobs....
Running ./lib/zmacs/zmacs --help indeed produces no output, but gives no error either.